Ebullient cooling device

ABSTRACT

An ebullient cooling device includes a chamber, a heat sink, a heat receiving member, and a heat dissipating member. The chamber includes a heat conducting plate with a heat generating body on an outer side surface thereof, and an airtight space filled with coolant that undergoes a phase change between liquid and gas, on an inner side of the heat conducting plate. The heat sink is provided on the outer side surface of the heat conducting plate. The heat receiving member is provided on an inner side surface of the heat conducting plate so as to oppose the heat generating body with the heat conducting plate sandwiched therebetween, and transfers heat generated at the heat generating body to the coolant. The heat dissipating member is provided on the inner side surface of the heat conducting plate, receives heat transferred by the coolant, and dissipates the heat to the heat sink.

TECHNICAL FIELD

The present invention relates to an ebullient cooling device that, in anelectronic device in which an LSI or IC is mounted, in particularsuppresses heat generation of the LSI or IC by utilizing the phasechange phenomenon of a coolant that is boiled and liquefied.

BACKGROUND ART

In an LSI and IC to be used in an electronic device such as a computeror the like, circuit integration is increasing in an accelerated mannerin each circuit generation. Moreover, in recent years, demands for areduction in size and thickness of devices are increasing. For thisreason, the heat generation density of LSIs and ICs is on track to keepincreasing from now on. In order to operate these LSIs and ICs at a highspeed and in a stable manner, it is necessary to control the operatingtemperature so as to be a given temperature or less. A cooling methodcompatible with the amount of heat of the LSI or IC is thereforeemployed. However, when attempting to reduce the size and thickness of adevice, for a cooler such as a heat sink that is to be mounted on theLSI or IC, the current situation is that it is not possible to secure asize that is compatible with the amount of heat generated.

Therefore, an ebullient cooling device has been proposed that includes aheat receiving plate 3, a heat transfer means 4, and a heat sink 5, asshown in FIG. 11. This small heat receiving plate 3 is arranged on aheat generating body 2 such as an LSI or IC that is installed on asubstrate 1, and absorbs the heat of that heat generating body 2. Theheat that the heat receiving plate 3 has absorbed is transported to theheat sink 5 that is mounted at a location of the substrate 1 wider thanthe heat generating body 2, via the heat transfer means 4.

As the aforementioned heat transfer means 4, a metal having high thermalconductivity such as aluminum and copper may be used. However, as theheat transfer means 4, it is preferable to use a heat pipe 6 that has amore outstanding heat transfer performance. This heat pipe 6 uses thephase change phenomenon in which a coolant gasifies at the heatreceiving plate 3 that is in contact with the heat generating body 2,and this gasified coolant liquefies at a heat dissipating plate 7 thatis provided under the heat sink 5. The heat pipe 6, utilizing this phasechange phenomenon, moves the heat that is generated at the heatgenerating body 2 such as an LSI or IC to the heat sink 5.

The structure of the heat pipe 6 shall be described referring to thecross-sectional pattern diagram of FIG. 12. This heat pipe 6 isconstituted by a hollow tube-shaped container 8 that is comprised by ametal having high heat conductivity such as aluminum or copper, and acoolant that is sealed inside this container 8. The heat receiving plate3 that is in contact with the heat generating body 2 such as an LSI orIC is coupled to one end portion of the heat pipe 6. The heatdissipating plate 7 that is in contact with the heat sink 5 serving as acooler is coupled to the other end portion of the heat pipe 6.

While the coolant undergoes a phase change from a liquid to a gas at theheat receiving plate 3, the coolant undergoes a phase change from a gasto a liquid at the heat dissipating plate 7. For this reason, in thiskind of heat pipe 6, the vaporized coolant that is produced at the heatreceiving plate 3 moves to the heat dissipating plate 7 side due to thepressure at the heat receiving plate 3 side being high. Also, the liquidcoolant that is produced at the heat dissipating plate 7 side circulatesto the heat receiving plate 3 by passing through a fine mesh called awick 9 that is attached to the inner face of the heat pipe 6. The gapsin the mesh are formed to be extremely narrow. By utilizing the surfacetension of the liquid coolant, the coolant passes through the gaps ofthe mesh and is circulated to the heat receiving plate 3 side. Byrepeating these phenomena, thermal transport with the heat pipe 6 isenabled. By utilizing the phase change of the coolant in this manner,the heat pipe 6 can achieve a far higher thermal conductivity comparedto metal such as aluminum or copper having a high thermal conductivity.

However, when circulating the liquefied coolant that is produced at theheat dissipating plate 7 to the heat receiving plate 3 by the heat pipe6, since it goes through the fine mesh wick 9, it is not possible toincrease the amount of heat transport. Accordingly, it is difficult tocool a heat generating body 2 having a large amount of heat.

For this reason, in Patent Document 1, an ebullient cooling device isproposed based on a method that boils a coolant with a heat-receivingplate, and circulates the liquid that is produced at a heat-dissipatingplate by gravity. In thermal transport that utilizes this boiling, thereis a characteristic of the thermal transport capability being larger dueto using more of the coolant than a heat pipe and circulating it bygravity. In Patent Document 1, a loop-shaped flow passage is formed in aflat plate. This constitution separates the flow passage through whichthe gas coolant passes and the flow passage through which the liquidcoolant that is produced at the heat dissipating plate circulates,reduces the pressure loss that occurs due to the collision between thetwo, and increases the equivalent thermal conductivity.

In Patent Document 2, the surface area of the heat receiving plate thatcomes into contact with the coolant is increased by placing a boilingpromotion structure at the heat receiving plate. By enhancing thethermal transmittance from the heating generating portion to thecoolant, boiling is promoted, and the equivalent thermal conductivity isincreased.

Patent Document 3 discloses a structure that provides fins having apartial cutaway in the heat dissipating wall, and so the surface areathat performs condensation is increased, and the equivalent thermalconductivity is increased by raising the condensation effect.

In Patent Document 4, a constitution is shown in which wave-shaped finshaving a low height are arranged in two stages (or three or morestages), with the wave-shaped fins being joined by matching thepositions of the bent-back parts so as to be able to mutually transmitheat.

In Patent Document 5, a constitution is shown in which chevron-shapedfirst fins are respectively arranged to the inner side of a heatreceiving plate and a heat dissipating plate, and chevron-shaped secondfins are arranged via a wire mesh support member or the like to theinner side of the first fins.

PRIOR ART DOCUMENTS Patent Documents

[Patent Document 1] Japanese Unexamined Patent Application, FirstPublication No. 2006-344636

[Patent Document 2] Japanese Unexamined Patent Application, FirstPublication No. H07-161888

[Patent Document 3] Japanese Unexamined Patent Application, FirstPublication No. 2000-74536

[Patent Document 4] Japanese Unexamined Patent Application, FirstPublication No. H10-209356

[Patent Document 5] Japanese Unexamined Patent Application, FirstPublication No. H11-31768

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

However, as shown in Patent Document 1, adopting a structure thatseparates the flow passages of the gas and liquid coolant for ebullientcooling as a method of increasing the equivalent thermal conductivity ofthe plate-shaped ebullient cooling device leads to the problem of thedesign of the flat plate used for ebullient cooling becomingcomplicated. That is to say, when the flow passages are separated, it isnecessary to finely adjust the flow passages of each device, and sogeneral versatility is impaired.

Also, as shown in Patent Documents 2 to 5, in methods of increasing thesurface area that is contact with the coolant via fins at the heatreceiving plate and the heat dissipating plate, it is only possible toincrease the region where boiling and condensation occurs by the amountof the increased surface area, and so it is not possible to expect alarge improvement in the equivalent thermal conductivity.

Moreover, in the technology that is disclosed in Patent Documents 2 to5, the fins that are arranged in the heat receiving plate and the heatdissipating plate (heat receiving member, heat dissipating member)interfere with each other. This has led to the problem of a drop in theefficiency of boiling and condensing the coolant.

The present invention has been achieved in view of the abovecircumstances. An exemplary object of the present invention is toprovide an ebullient cooling device that can efficiently perform heatdissipation with a simple constitution, and be compatible with LSIs andICs having a large amount of heat generation.

Means for Solving the Problem

In order to solve the aforementioned issues, an ebullient cooling deviceof the present invention includes a chamber, a heat sink, a heatreceiving member, and a heat dissipating member. The chamber includes aheat conducting plate with a heat generating body provided on an outerside surface thereof, and an airtight space provided on an inner side ofthe heat conducting plate, the airtight space filled with a coolant thatundergoes a phase change between liquid and gas. The heat sink isprovided on the outer side surface of the heat conducting plate. Theheat receiving member is provided on an inner side surface of the heatconducting plate so as to oppose the heat generating body with the heatconducting plate sandwiched therebetween, and transfers heat generatedat the heat generating body to the coolant. The heat dissipating memberis provided on the inner side surface of the heat conducting plate,receives the heat transferred by the coolant, and dissipates the heat tothe heat sink. The heat receiving member and the heat dissipating memberare arranged spaced apart from each other in a surface direction of theheat conducting plate. The heat receiving member is immersed in thecoolant in a liquid state.

Effect of the Invention

According to the present invention, the coolant that is sealed in theairtight space of the chamber undergoes a phase change between liquidand gas between the heat receiving member and the heat dissipatingmember, whereby it is possible to transport the heat that is generatedat the heat generating body to the heat sink. Also, the heat receivingmember and the heat dissipating member are arranged spaced apart fromeach other in the surface direction of the heat conducting plate. Thatis to say, the heat receiving member and the heat dissipating member arearranged in a positional relation of not facing each other. For thatreason, it is possible to maintain the heat conduction efficiency at ahigh level without the movement of the coolant that becomes a gas at theheat receiving member being impeded. Accordingly, it is possible toefficiently dissipate heat with a simple structure, and it is possibleto make it compatible with LSIs and ICs having a large amount of heatgeneration.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of an ebullient cooling deviceaccording to a first exemplary embodiment of the present invention.

FIG. 2 is an exploded perspective view of the ebullient cooling deviceshown in FIG. 1 seen from the reverse side.

FIG. 3 is a longitudinal cross-sectional view of the ebullient coolingdevice according to the first exemplary embodiment of the presentinvention.

FIG. 4 is an exploded perspective view of an ebullient cooling deviceaccording to a second exemplary embodiment of the present invention.

FIG. 5 is an exploded perspective view of an ebullient cooling deviceaccording to a third exemplary embodiment of the present invention.

FIG. 6 is a longitudinal cross-sectional view of an ebullient coolingdevice according to a fourth exemplary embodiment of the presentinvention.

FIG. 7 is a longitudinal cross-sectional view of an ebullient coolingdevice according to a fifth exemplary embodiment of the presentinvention.

FIG. 8 is a perspective view of an ebullient cooling device according toa sixth exemplary embodiment of the present invention.

FIG. 9 is a longitudinal cross-sectional view of the ebullient coolingdevice according to the sixth exemplary embodiment of the presentinvention.

FIG. 10 is a transparent elevational view for describing the flow of acoolant in the ebullient cooling device according to the sixth exemplaryembodiment of the present invention.

FIG. 11 is a perspective view of a conventional ebullient coolingdevice.

FIG. 12 is a cutaway view that shows the internal structure of a heatpipe.

EMBODIMENTS FOR CARRYING OUT THE INVENTION First Exemplary Embodiment

A first exemplary embodiment of the present invention shall be describedwith reference to FIG. 1 to FIG. 3.

FIG. 1 to FIG. 3 show an ebullient cooling device 20 according to thefirst exemplary embodiment of the present invention. A heat generatingbody 10 which is an LSI or IC, for example is joined to the ebullientcooling device 20. More specifically, the heat generating body 10 isjoined to a heat receiving plate 22 of the ebullient cooling device 20by a thermally conductive grease or a thermally conductive sheet. Atthis time, the heat generating body 10 may be bonded with solder.

The ebullient cooling device 20 has a plate-shaped hollow chamber 24.This chamber 24 has a side wall portion 21 that is formed in the shapeof a quadrilateral frame, a heat receiving plate (heat conducting plate)22 that covers an upper opening 21A of the side wall portion 21, and aheat dissipating plate (heat conducting plate) 23 that covers a loweropening 21B of the side wall portion 21.

The heat receiving plate 22 and the heat dissipating plate 23 are formedwith a metal such as copper or aluminum having high thermalconductivity. The heat receiving plate 22 and the heat dissipating plate23 are arranged to face each other in the thickness direction of thechamber 24. Due to the upper opening 21A and the lower opening 21B ofthe side wall portion 21 being blocked by the heat receiving plate 22and the heat dissipating plate 23, an airtight space is formed withinthe side wall portion 21. A coolant C is filled in this airtight space.As this coolant C, a liquid coolant C1 and a gas coolant C2 coexist inthe airtight space. The coolant C can undergo a phase change betweenliquid and gas.

A coolant injection port 21C for injecting the coolant C into theairtight space is provided in the side wall portion 21 of the chamber24.

After separately manufacturing the side wall portion 21, the heatreceiving plate 22, and the heat dissipating plate 23, the chamber 24may be formed by joining them by brazing or the like. Alternatively, thechamber 24 may be formed by integrally forming either one of the heatreceiving plate 22 and the heat dissipating plate 23 with the side wallportion 21. An O-ring 25 may be arranged at the periphery of the upperopening 21A and the periphery of the lower opening 21B of the side wallportion 21. The upper opening 21A and the lower opening 21B may beblocked by the heat dissipating plate 23 and the heat receiving plate 22via this O-ring 25, and moreover, the heat dissipating plate 23 and theheat receiving plate 22 may be attached to the side wall portion 21 byscrews or the like. In this way, in the case of using the O-ring 25,removal of the heat receiving plate 22 and the heat dissipating plate 23is easy. As a result, it is possible to improve the workability whenmounting the heat generating body 22 and a heat sink 28 described later.

The heat generating body 10 such as an LSI or IC that serves as a heatsource is arranged on the outer surface of the airtight space at theheat receiving plate 22. A heat receiving member 26 is fixed on theinside surface of the location on the heat receiving plate 22 where theheat generating body 10 is arranged. The heat receiving member 26transmits heat that is produced by the heat generating body 10 to thecoolant C.

The heat receiving member 26 is constituted by a plurality of fins thatare arranged and fixed at a specified interval on the inside surface ofthe heat receiving plate 22. The plurality of fins (pin fins in thepresent exemplary embodiment) are comprised by cuboid rectangular finsor pin fins with their surfaces roughened in order to promote boiling.

In the case of installing a plurality of heat generating bodies 10 onthe outer surface of the heat receiving plate 22, heat receiving members26 are arranged at locations corresponding to the heat generating bodies10 or in the vicinity thereof. It is preferable for the heat receivingmember 26 to be integrally molded with the heat receiving plate 22 bymachining or forging in order to reduce thermal resistance. On the otherhand, from the viewpoint of productivity, it is preferable to separatelymanufacture the plurality of fins that constitute the heat receivingmember 26, and braze them to the heat dissipating plate 23.

In the heat receiving member 26 that is composed of pin fins, theplurality of pin fins are arranged in a matrix pattern in order to asmuch as possible not impede the flow of the gasified coolant C1 and thecoolant C2 that is liquefied and flowed back. In order for theseparation of air bubbles that are generated during boiling at the heatreceiving member 26 to be undisturbed, it is preferable to ensure theinterval between the pin fins is from 1 mm to several millimeters. Inthe case of using rectangular fins that are composed of cuboid members,from the viewpoint of increasing surface area, it is conceivable toinstall more fins by reducing the thickness. On the other hand, in thecase of the fins being thinner, due to the thermal capacity of the finsbeing less, it is not preferable from the viewpoint of coolingefficiency. Moreover, in the case of the fins being thin, fabrication isdifficult. Therefore, it is desirable for the fins to at least have athickness of 1 mm to several millimeters.

The height of the fins, that is to say, the height from the insidesurface of the heat receiving plate 22 at the heat receiving member 26is preferably set to the dimension of approximately one-half of thethickness of the chamber 24, that is to say, the facing distance betweenthe heat receiving plate 22 and the heat dissipating plate 23 (thedistance between the heat receiving plate 22 and the heat dissipatingplate 23). This is in order to immerse the entirety of the heatreceiving member 26 in the liquid coolant C1 to make use of the entiresurface area of the fins for boiling.

It is preferable that a roughening process be performed on each fin ofthe heat receiving member 26, with the surface roughening being in theroughness range of 1 μm to 100 μm. Thereby, it is possible to form onthe surface of the heat receiving member 26 a plurality of sharpangled-shapes that serve as nuclei when bubbles are produced by the heatreception of the coolant C1. As a result, it is possible to promoteboiling of the liquid coolant C at the surface of the heat receivingmember 26.

A heat dissipating member 27 for snatching heat from the gasifiedcoolant C2 is provided on the inner side of the heat dissipating plate23. This heat dissipating member 27 is installed spaced apart from theheat receiving member 26 in the surface direction of the heat receivingplate 22 and the heat dissipating plate 23 (that is to say, in thedirection perpendicular to the thickness direction of the heat receivingplate 22 and the heat dissipating plate 23). That is to say, the heatdissipating member 27 is arranged so as not to be mutually opposed tothe heat receiving member 26. The heat sink 28 is provided as a coolingdevice at the outside surface of the location on the heat dissipatingplate 23 where the heat dissipating member 27 is arranged.

This heat sink 28 may be integrally molded with the heat dissipatingplate 23 by machining or forging. Alternatively, after separatelymanufacturing the heat sink 28 from the heat radiating plate 23, bothmay be connected with a thermally conductive grease or a thermallyconductive sheet and the like.

The heat dissipating member 27 is constituted by a plurality of finsthat are arranged at a fixed interval. The plurality of pins arecomposed of a plurality of cuboid members or pin fins (pin fins in thepresent exemplary embodiment) that have been subjected to surfaceroughening in order to promote condensation of the coolant C2 that hasbecome a gas. At the heat receiving member 26 that are composed of thepin fins, a plurality of the pin fins are preferably arranged in amatrix pattern in order to increase the flowability of the coolant C.

The coolant C to be filled in the chamber 24 may be water, which is easyto obtain. In the case of being used in an electronic device, it ispreferable to use an organic coolant that has insulation properties.This is so that, in the event of the coolant C coming into contact withelectronic components or the substrate in the case of a leakage of thecoolant C, it has no effect on those electronic components or thesubstrate, and they can be reused. Moreover, many organic coolants havea lower surface tension than water, and so their boiling point is lowerthan water. For this reason, it is possible to keep the temperature ofthe heat generating body 10 lower than the boiling point of water.

After pouring the coolant C in the chamber 24, by creating a vacuum inthe interior of the chamber 24, it is possible to make the boiling pointlower. As a result, it is possible to maintain the temperature of theheat generating body at an even lower temperature. After creating avacuum in the interior of the chamber 24, the coolant injection port 21Cis caulked and hermetically sealed. Alternatively, the interior may behermetically sealed by plugging the coolant injection port 21C with anattachment stopper.

Regarding the positional relation of the heat receiving member 26 andthe heat dissipating member 27, as stated above, the heat receivingmember 26 and the heat dissipating member 27 are installed spaced apartin the surface direction of the heat receiving plate 22 and the heatdissipating plate 23. That is to say, the heat dissipating member 27 isnot provided directly above the heat receiving member 26. The reason forthis is that when the heat receiving member 26 and the heat dissipatingmember 27 are in close proximity, the gas produced by the heat receivingmember 26 immediately has its heat snatched away by the heat dissipatingplate, causing droplets being produced, and this becomes a loss ofpressure and impedes the movement of the gas that is produced by theheat receiving member 26. The separation distance of the heat receivingmember 26 and the heat dissipating member 27 is preferably at leastequal to or more than the width dimension of the heat generating body10.

The height of the heat receiving member 26 is preferably set so as to bespaced 1 mm or more away from the facing surface of the heat dissipatingplate 23 that is oppositely positioned, in consideration of the heatconduction efficiency to the coolant C. In the same way, the height ofthe heat dissipating member 27 is preferably set so as to be spaced 1 mmor more away from the facing surface of the heat receiving plate 22 thatis oppositely positioned, in consideration of the heat conductionefficiency to the coolant C.

Next, action of the ebullient cooling device 20 of the present exemplaryembodiment shall be described in detail.

The coolant C that is sealed in the chamber 24 becomes a saturated vaporpressure due to the creation of the vacuum, and so its reaches boilingpoint at room temperature. The saturated vapor pressure is the maximumpressure that occurs in a space at a certain temperature, in a sealedspace in which only a substance such as water exists. Thereby, in theairtight space within the chamber 24, the liquid coolant C1 and the gascoolant C2 coexist. The liquid coolant C1 exists at the lower portion ofthe airtight space, while the gas coolant C2 exists in the upper portionof the airtight space.

When the heat generating body 10 such as an LSI or IC generates heat,the heat passes through the heat receiving plate 22 and reaches the heatreceiving member 26 in the chamber 24, and imparts the heat to theliquid coolant C1 surrounding the heat receiving member 26. When thecoolant C1 that has been heated reaches boiling point, air bubbles areformed, with the sharp-angled shapes serving as nuclei.

When the heat is additionally imparted from the heat receiving member 26to the liquid coolant C1, the bubbles develop. When the bubbles become acertain size, the buoyant force of the bubbles becomes greater than theabsorbing power of the surface of the heat receiving member 26 due tothe surface tension. As a result, the bubbles separate. At this time,since the space of the region where the bubbles had existed is released,the surrounding liquid coolant C1 flows in, and new boiling starts tooccur.

As described above, due to the surface roughing process that isperformed on the surface of the heat receiving member 26, numeroussharp-angled shapes exist, and so boiling occurs over the entire finsurface in the heat receiving member 26. By this boiling, the liquidcoolant C1 undergoes a phase change to the gas coolant C2. At this time,the volume of the coolant C increases several hundred times, and so thepressure of the airtight space in the chamber 24 rises. Thereby, the gascoolant C2 moves to the upper heat dissipating member 27 side. In thisway, the gas coolant C2 that has moved to the heat dissipating member 27has its heat snatched by contact with the fins of the heat dissipatingmember 27 and condenses. Thereby, drops are generated centered on nucleiat the sharp-angled shapes that are formed on the surface of the fins.

When the drops grow and the gravity of those drops become greater thanthe absorbing power due to the surface tension of the heat dissipatingmember 27, the drops head downward from the heat dissipating member 27and separate. Due to this separation, since the region where the dropshad been adhering is made available, the gas coolant C makes contactwith the fin surface of the heat dissipating member 27, and newcondensation occurs. Since the surface roughening treatment has beenperformed on the fin surfaces that constitute the heat dissipatingmember 27, numerous sharp-angled shapes exist, and so condensationoccurs over all the fins of the heat dissipating member 27.

The drops that are produced by condensation at the heat dissipatingmember 27 are returned to the liquid coolant C1 that exists below theheat dissipating member 27, and furthermore by being transported to theheat receiving member 26, the liquid coolant C1 again undergoes a phasechange to the gas coolant C2. On the other hand, the heat that wassnatched away from the gas coolant C1 at the heat dissipating member 27is released into the air via the heat sink 28 that is attached to theouter surface of the chamber 24.

In this manner, by utilizing the phase change and volumetric change ofthe coolant C, the coolant C is made to move while producing a pressuredifferential between the heat receiving member 26 and the heatdissipating member 27, whereby it is possible to obtain a thermaltransport capability ranging from several times to several hundred timescompared to copper, which is a metal with good heat conductionefficiency.

Also, the heat receiving member 26 and the heat dissipating member 27are arranged spaced mutually apart in the surface direction of the heatreceiving plate 22 and the heat dissipating plate 23, that is, in apositional relation of not facing each other. For this reason, the heatreceiving member 26 and the heat dissipating member 27 are not affectedby each other, and optimal and unrestricted setting of the contactposition with the coolant and the contact surface area becomes possible.

In the case of the heat receiving member 26 and the heat dissipatingmember 27 being in close proximity, the gas that is produced by the heatreceiving member 26 has its heat snatched away by the heat dissipatingmember 27 that is located nearby, and so drops may be produced.

In contrast, in the ebullient cooling device 20 of the present exemplaryembodiment, the heat receiving member 26 and the heat dissipating member27 are arranged in a positional relation of not facing each other. Forthis reason, it is possible to prevent a reduction in the heatconduction efficiency as a result, without impeding the flow of the gasthat is produced by the heat receiving member 26.

In the ebullient cooling device 20 that is shown in the presentexemplary embodiment as described in detail hereinabove, the coolant Cthat is sealed in the airtight space of the chamber 24 is made to changephase to liquid/gas between the heat receiving member 26 and the heatdissipating member 27. Thereby, it is possible to efficiently convey theheat that is produced at the heat generating body 10 to the heat sink28. Also, the heat receiving member 26 and the heat dissipating member27 are arranged spaced apart in the surface direction of the heatreceiving plate 22 and the heat dissipating plate 23. That is to say,the heat receiving member 26 and the heat dissipating member 27 arearranged in a positional relation of not facing each other. With thisconstitution, it is possible to maintain the heat conduction efficiencyat a high level without the movement of the coolant C1 that becomes agas being impeded at the heat receiving member 26. Accordingly, it ispossible to efficiently dissipate heat with a simple constitution, andcompatibility with a heat generating body 10 having a large amount ofheat generation becomes possible.

Also, along with the heat receiving plate 22 and the heat dissipatingplate 23 being arranged facing each other, the heat generating body 10and the heat receiving member 26 are provided on the heat receivingplate 22, and the heat dissipating member 27 and the heat sink 28 areprovided on the heat dissipating plate 23. With this constitution, it ispossible to reliably cause the coolant C to change phase to a liquid/gasbetween the heat receiving member 22 and the heat dissipating member 23.

If the heat that is produced by the heat generating body 10 such as anLSI or IC that is mounted at a high heat generation density is notimmediately transported away, its temperature rises and a malfunctionoccurs, and according to the circumstances, will be a factor leading toloss of operation. With regard to this point, in the present exemplaryembodiment, by raising the equivalent thermal conductivity, it ispossible to rapidly transport the heat that is produced at the heatgenerating body 10. Thereby, even if the heat generating body 10 ismounted at a high heat generation density, that heat efficientlydiffuses without remaining at a particular location, and so it ispossible to lower the temperature of the heat generating body 10.

Also, there is no need to separate the flow passage of the coolant C1 inwhich a phase change is performed between the heat receiving plate 22and the heat dissipating plate 23. That is to say, there is no need toconsider a coolant transfer path from the heat receiving plate 22 to theheat dissipating plate 23, and a coolant transfer path from the heatdissipating plate 23 to the heat receiving plate 22. When consideringsuch coolant transfer paths, fine adjustment is required each time thedesign is modified. However, in the present exemplary embodiment,consideration need only be given to the placement of the heat receivingplate 22 and the heat dissipating plate 23. Accordingly, no designdifficulties arise, and it is possible to simplify the overallconfiguration.

In addition, in the aforementioned ebullient cooling device 20, by usinga heat transport device having a flat plate shape, heat transportsimultaneously from a plurality of heat generating bodies becomespossible. For this reason, a plurality of components for transportingheat becomes unnecessary. Moreover, it becomes possible to consolidate aplurality of cooling devices such as heat sinks that had been neededinto one, and so it is possible to eliminate heat sinks and fans.Thereby, a reduction in size and thickness of an entire device becomespossible.

Second Exemplary Embodiment

Next, a second exemplary embodiment of the present invention shall bedescribed with reference to FIG. 4.

In the ebullient cooling device 20 of the first exemplary embodimentdescribed above, the heat receiving member 26 is constituted by aplurality of columnar pin fins with their surfaces roughened beingprovided on the heat receiving plate 22 on which the heat generatingbody 10 is arranged. The heat receiving member 26 may also beconstituted with rectangular fins 30 in which a plurality of cuboidmembers are arranged at a fixed interval as shown in FIG. 4.

In the heat receiving member 26 that is constituted with thisrectangular fin, it is constituted with cuboid members that have theirsurfaces roughened, and overall is formed in a comb-like shape.

Although the greater the surface area of the heat receiving member 26that is in contact with the coolant C, the better, the surface area incontact with the liquid coolant C and the boiling performance are notproportional. When the pin fin of the first exemplary embodiment isreplaced with the rectangular fin 30, it has been confirmed that thesurface area in contact with the coolant C decreases, but the boilingperformance does not significantly decrease. Also, in terms ofproductivity, the rectangular fin 30 is more advantageous than the pinfin. The rectangular fin 30 may be manufactured by machining or forging.Alternatively, after separately manufacturing the cuboid members of therectangular fins 30, they may be welded by brazing or the like to theheat receiving plate 22, and then a process of roughening the surface toa roughness of 1 μm to 100 μm may be performed. This kind of rectangularfin 30 may also be applied to the heat dissipating member 27 that isconnected to the heat sink 28.

Third Exemplary Embodiment

Next, a third exemplary embodiment of the present invention shall bedescribed with reference to FIG. 5.

In the ebullient cooling device 20 of the first exemplary embodiment, aplurality of columnar pin fins with their surfaces roughed are made toserve as heat receiving member 26 on the heat receiving plate 22 onwhich the heat generating body 10 is arranged. The heat receiving member26 may also be constituted with a cuboid-shaped heat dissipating block31 that has its surfaces roughened as shown in FIG. 5.

Even if this heat receiving member 26 is formed in a block shape, thereis no significant drop in the boiling performance.

When considering the productivity, a block shape is easier tomanufacture than a pin fin or rectangular fin, and so is advantageous interms of manufacturing. This heat receiving member 26 may bemanufactured integrally with the heat receiving plate 22 by machining orforging. Alternatively, a block that is separately fabricated may bewelded to the heat receiving plate 22 by brazing or the like, and thensubjected to a process of roughening its surfaces to a roughness of 1 μmto 100 μm.

This kind of heat radiating block 31 may also be applied to the heatdissipating member 27 that is connected to the heat sink 28.

Fourth Exemplary Embodiment

Next, a fourth exemplary embodiment of the present invention shall bedescribed with reference to FIG. 6.

In the ebullient cooling device 20 of the first exemplary embodiment,the chamber 24 is arranged so as to be horizontal, but it is not limitedthereto. The ebullient cooling device 20 may also be arranged in avertical manner as shown in FIG. 6. That is to say, the heat receivingmember 26 and the heat dissipating member 27 may be positioned so as tobe in a positional relation in which the normal of the heat receivingmember 26 and the heat dissipating member 27 is perpendicular to theheat receiving plate 22 and the heat dissipating plate 23 in thevertical direction. In this case, among the heat receiving member 26 andthe heat dissipating member 27, at least the heat receiving member 26 isimmersed in the liquid coolant C1. With such a constitution, it ispossible to increase the degree of freedom of the design.

In the example of the ebullient cooling device 20 shown in FIG. 6, theheat receiving member 26 that is connected to the heat generating body10 is, in the vertical direction, provided lower than the heatdissipating member 27 that is connected to the heat sink 28. With such aconstitution, the heat receiving member 26 that receives the heat of theheat generating body 10 generates bubbles by causing the coolant C1 toundergo a phase change by transmitting heat to the liquid state coolantC1. Here, the bubbles that are generated move upward in the verticaldirection by the buoyant force, and by making contact with the heatdissipating member 27 that is connected to the heat sink 28, the heat issnatched away. Thereby, the gas coolant C2 condenses and becomes drops.

Regarding the positional relation of the heat receiving member 26 andthe heat dissipating member 27, the heat dissipating member 27 may bebelow with respect to the heat receiving member 26, or the heatdissipating member 27 may be above with respect to the heat receivingmember 26.

However, at the least, it is necessary to pour in the coolant C to theheight of the heat receiving member 26, so as to immerse the heatreceiving member 26 in the liquid coolant C1. Thereby, regardless of thepositional relationship, the heat receiving member 26 on which the heatgenerating body 10 is mounted is immersed in the liquid coolant C.Boiling occurs due to the heat receiving member 26, circulation occursutilizing the phase change, and the heat is transmitted through theentire chamber 24, and dissipated via the heat sink 28.

Fifth Exemplary Embodiment

Next, a fifth exemplary embodiment of the present invention shall bedescribed with reference to FIG. 7.

In the ebullient cooling device 20 of the aforementioned first exemplaryembodiment, the heat receiving member 26 is arranged on the heatreceiving plate 22 that constitutes the chamber 24, and the heatdissipating member 27 is arranged on the heat dissipating plate 23 thatfaces the heat receiving plate 22. In this fifth exemplary embodiment,as shown in FIG. 7, the heat receiving member 26 and the heatdissipating member 27 may be arranged on one heat conducting plate 32.

By adopting this heat conducting plate 32, it is possible to improveproductivity by reducing the overall number of components due to membersharing. This heat conducting plate 32 is constituted with for examplemetal. The heat of the heat generating body 10, by being transferredthrough that metal, migrates from the heat receiving member 26 to theheat dissipating member 27, and it is possible to exhibit a synergisticeffect combined with the heat transport via the coolant C.

This heat-receiving heat-dissipating member 32 may be fabricated bymachining or forging. Alternatively, fins of the heat receiving member26 and the heat dissipating member 27 that are separately manufacturedmay be attached by brazing. A sealing plate 33 that is arranged so as toface the heat conducting plate 32 may be made with aluminum or cooperwith good thermal conductivity, and in consideration of productivity,may be made from a resin such as acrylic.

Sixth Exemplary Embodiment

Next, a sixth exemplary embodiment of the present invention shall bedescribed with reference to FIG. 8 to FIG. 10.

In the ebullient cooling device 20 of the aforementioned first exemplaryembodiment, the chamber 24 is arranged to be horizontal, but it is notlimited thereto. As shown in FIG. 8 to FIG. 10, in the sixth exemplaryembodiment, the ebullient cooling device 10 may be arranged in avertical manner as shown in FIG. 9 and FIG. 10, and a buffer tank 40 maybe arranged at the upper position thereof.

That is to say, in the case of the heat generating body 10 beingarranged in the vicinity of the upper end of the heat sink 28 in thevertical direction, it is necessary to immerse the heat receiving member26 that is connected to the heat generating body 10 in the liquidcoolant C1. Thereby, the liquid coolant C1 comes to occupy the greaterpart of the interior of the chamber 24. However, when the liquid coolantC1 occupies the greater part of the interior space of the chamber 24,due to the phase transition at the heat receiving member 26, the liquidcoolant C1 is converted to the gas coolant C2, whereby its volumeincreases. Thereby, the space that can accommodate the coolant Cdisappears, and the pressure within the chamber 24 rises more thannecessary. In this case, since the boiling point of the coolant C rises,there is the risk of no longer being able to cool the heat generatingbody 10 to a predetermined temperature.

In order to suppress this kind of increase in the internal pressure,that which becomes an evacuation space of the gas coolant C2 is thebuffer tank 40 that is shown in FIG. 8 to FIG. 10. This buffer tank 40is arranged at the upper portion of the heat dissipating plate 23 so asto project out. A buffer space for accommodating the gas coolant C2 isformed within the buffer tank 40. This buffer tank 40 is arranged at theupper portion of the heat dissipating plate 23 in the verticaldirection, and above the heat sink 28. On the other hand, the heatreceiving member 26 that is connected to the heat generating body 10 isarranged at the opposing position of the buffer tank 40.

FIG. 10 shows the sequence diagram of the coolant C at this time. At theheat receiving member 26 that is connected to the heat generating body10, the liquid coolant C1 boils and gas bubbles are produced. When thosegas bubbles separate from the heat receiving member 26, the space thatthe gas bubbles (the gas coolant C1) occupies is released, and theliquid coolant C2 flows into that space, whereby circulation occurs.Thereby, the heat of the heat generating body 10 is dispersed throughoutthe chamber 24, and dissipated into the air by the heat sink 28 that ismounted on the heat dissipating member 27 at the lower portion in thevertical direction.

At this time, gas that is produced by the heat receiving member 26 isaccommodated in the internal space of the buffer tank 40 that isinstalled at the upper portion of the heat dissipating plate 23. As aresult, it is possible to inhibit a rise in the internal pressure of thechamber 24, and derive a cooling effect for the heat generating body 10that is installed on the upper portion of the chamber 24. Also, in thecase of the amount of heat of the heat generating body 10 being large,since more of the liquid coolant C2 boils more liquid coolant C2 needsto be present in the vicinity of the heat receiving member 26. In thatcase, by compensating for the coolant C that is lacking by storingcoolant C in a portion of the buffer tank 40, it can be compatible alsowith the heat generating body 10 having a large amount of heatgeneration.

The exemplary embodiments of the present invention have been describedin detail hereinabove with reference to the drawings, but specificconstitutions are not limited to these exemplary embodiments, and designmodifications and the like that does not depart from the scope of thepresent invention are also included.

This application is based upon and claims the benefit of priority fromJapanese patent application No. 2010-115539, filed May 19, 2010, thedisclosure of which is incorporated herein in its entirety by reference.

INDUSTRIAL APPLICABILITY

The present invention can be applied to an ebullient cooling device.With this ebullient cooling device, it is possible to suppress the heatgeneration of LSIs and ICs by utilizing the phase change phenomenon of acoolant that boils and liquefies.

DESCRIPTION OF REFERENCE SYMBOLS

-   10 Heat generating body-   20 Ebullient cooling device-   21 Side plate portion-   22 Heat receiving plate-   23 Heat dissipating plate-   24 Chamber-   26 Heat receiving member-   27 Heat dissipating member-   28 Heat sink-   32 Heat conducting plate-   C1 (C) Liquid coolant-   C2 (C) Gas coolant

1. An ebullient cooling device comprising: a chamber that includes a heat conducting plate with a heat generating body provided on an outer side surface thereof, and an airtight space provided on an inner side of the heat conducting plate, the airtight space filled with a coolant that undergoes a phase change between liquid and gas; a heat sink that is provided on the outer side surface of the heat conducting plate; a heat receiving member that is provided on an inner side surface of the heat conducting plate so as to oppose the heat generating body with the heat conducting plate sandwiched therebetween, the heat receiving member transferring heat generated at the heat generating body to the coolant; and a heat dissipating member that is provided on the inner side surface of the heat conducting plate, the heat dissipating member receiving the heat transferred by the coolant, and dissipating the heat to the heat sink, the heat receiving member and the heat dissipating member arranged spaced apart from each other in a surface direction of the heat conducting plate, and the heat receiving member immersed in the coolant in a liquid state.
 2. The ebullient cooling device according to claim 1, wherein: the heat conducting plate is a heat receiving plate and a heat dissipating plate that are arranged facing each other with the airtight space sandwiched therebetween; the heat generating body and the heat receiving member are provided on the heat receiving plate; and the heat sink and the heat dissipating member are provided on the heat dissipating plate.
 3. The ebullient cooling device according to claim 2, wherein a height of the heat receiving member from the heat receiving plate and a height of the heat dissipating member from the heat dissipating plate are respectively set to a dimension of approximately one-half a distance between the heat receiving plate and the heat dissipating plate.
 4. The ebullient cooling device according to claim 2, wherein: the heat receiving member is spaced at least 1 mm or more from an inner side surface of the heat dissipating plate; and the heat dissipating member is spaced at least 1 mm or more from an inner side surface of the heat receiving plate.
 5. The ebullient cooling device according to claim 1, wherein the heat receiving member and the heat dissipating member include a plurality of fins that are installed in a standing manner on the inner side surface of the heat conducting plate.
 6. The ebullient cooling device according to claim 1, wherein the heat receiving member and the heat dissipating member are cuboid blocks fixed to the inner side surface of the heat conducting plate.
 7. The ebullient cooling device according to claim 1, wherein surface roughening of a surface roughness range of 1 μm to 100 μm is carried out on a surface of the heat receiving member and the heat dissipating member.
 8. The ebullient cooling device according to claim 1, wherein the chamber includes a buffer tank in which the coolant in a gas state flows in.
 9. The ebullient cooling device according to claim 1 wherein the heat receiving member and the heat dissipating member are immersed in the coolant of the liquid state. 